1GETSUBOPT(P) POSIX Programmer's Manual GETSUBOPT(P)
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6 getsubopt - parse suboption arguments from a string
7
9 #include <stdlib.h>
10 int getsubopt(char **optionp, char * const *keylistp, char **valuep);
12
15 The getsubopt() function shall parse suboption arguments in a flag
16 argument. Such options often result from the use of getopt().
17 The getsubopt() argument optionp is a pointer to a pointer to the
19 option argument string. The suboption arguments shall be separated by
20 commas and each may consist of either a single token, or a token-value
21 pair separated by an equal sign.
22 The keylistp argument shall be a pointer to a vector of strings. The
24 end of the vector is identified by a null pointer. Each entry in the
25 vector is one of the possible tokens that might be found in *optionp.
26 Since commas delimit suboption arguments in optionp, they should not
27 appear in any of the strings pointed to by keylistp. Similarly, because
28 an equal sign separates a token from its value, the application should
29 not include an equal sign in any of the strings pointed to by keylistp.
30 The valuep argument is the address of a value string pointer.
32 If a comma appears in optionp, it shall be interpreted as a suboption
34 separator. After commas have been processed, if there are one or more
35 equal signs in a suboption string, the first equal sign in any subop‐
36 tion string shall be interpreted as a separator between a token and a
37 value. Subsequent equal signs in a suboption string shall be inter‐
38 preted as part of the value.
39 If the string at *optionp contains only one suboption argument (equiva‐
41 lently, no commas), getsubopt() shall update *optionp to point to the
42 null character at the end of the string. Otherwise, it shall isolate
43 the suboption argument by replacing the comma separator with a null
44 character, and shall update *optionp to point to the start of the next
45 suboption argument. If the suboption argument has an associated value
46 (equivalently, contains an equal sign), getsubopt() shall update *val‐
47 uep to point to the value's first character. Otherwise, it shall set
48 *valuep to a null pointer. The calling application may use this infor‐
49 mation to determine whether the presence or absence of a value for the
50 suboption is an error.
51 Additionally, when getsubopt() fails to match the suboption argument
53 with a token in the keylistp array, the calling application should
54 decide if this is an error, or if the unrecognized option should be
55 processed in another way.
56
58 The getsubopt() function shall return the index of the matched token
59 string, or -1 if no token strings were matched.
60
62 No errors are defined.
63 The following sections are informative.
65
67 #include <stdio.h>
68 #include <stdlib.h>
69 int do_all;
72 const char *type;
73 int read_size;
74 int write_size;
75 int read_only;
76 enum
79 {
80 RO_OPTION = 0,
81 RW_OPTION,
82 READ_SIZE_OPTION,
83 WRITE_SIZE_OPTION
84 };
85 const char *mount_opts[] =
88 {
89 [RO_OPTION] = "ro",
90 [RW_OPTION] = "rw",
91 [READ_SIZE_OPTION] = "rsize",
92 [WRITE_SIZE_OPTION] = "wsize",
93 NULL
94 };
95 int
98 main(int argc, char *argv[])
99 {
100 char *subopts, *value;
101 int opt;
102 while ((opt = getopt(argc, argv, "at:o:")) != -1)
105 switch(opt)
106 {
107 case 'a':
108 do_all = 1;
109 break;
110 case 't':
111 type = optarg;
112 break;
113 case 'o':
114 subopts = optarg;
115 while (*subopts != '\0')
116 switch(getsubopt(&subopts, mount_opts, &value))
117 {
118 case RO_OPTION:
119 read_only = 1;
120 break;
121 case RW_OPTION:
122 read_only = 0;
123 break;
124 case READ_SIZE_OPTION:
125 if (value == NULL)
126 abort();
127 read_size = atoi(value);
128 break;
129 case WRITE_SIZE_OPTION:
130 if (value == NULL)
131 abort();
132 write_size = atoi(value);
133 break;
134 default:
135 /* Unknown suboption. */
136 printf("Unknown suboption `%s'\n", value);
137 break;
138 }
139 break;
140 default:
141 abort();
142 }
143 /* Do the real work. */
146 return 0;
149 }
150 Parsing Suboptions
152 The following example uses the getsubopt() function to parse a value
153 argument in the optarg external variable returned by a call to
154 getopt().
155 #include <stdlib.h>
158 ...
159 char *tokens[] = {"HOME", "PATH", "LOGNAME", (char *) NULL };
160 char *value;
161 int opt, index;
162 while ((opt = getopt(argc, argv, "e:")) != -1) {
165 switch(opt) {
166 case 'e' :
167 while ((index = getsubopt(&optarg, tokens, &value)) != -1) {
168 switch(index) {
169 ...
170 }
171 break;
172 ...
173 }
174 }
175 ...
176
178 None.
179
181 None.
182
184 None.
185
187 getopt() , the Base Definitions volume of IEEE Std 1003.1-2001,
188 <stdlib.h>
189
191 Portions of this text are reprinted and reproduced in electronic form
192 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
193 -- Portable Operating System Interface (POSIX), The Open Group Base
194 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
195 Electrical and Electronics Engineers, Inc and The Open Group. In the
196 event of any discrepancy between this version and the original IEEE and
197 The Open Group Standard, the original IEEE and The Open Group Standard
198 is the referee document. The original Standard can be obtained online
199 at http://www.opengroup.org/unix/online.html .
200IEEE/The Open Group 2003 GETSUBOPT(P)